The present invention relates to methods and apparatus to form a butt splice between adjacent ends of webs of material. Specifically such butt splices are usable to join together the leading end of a web from a new roll of material to a trailing end of a web which is from an expiring roll of material and which is being run, downstream from the expiring roll, under tension along a predetermined path of travel that includes a running web storage means. More particularly, the present invention relates to methods and apparatus to form a butt splice of the type described where the new and expiring rolls are supported on a roll unwind stand, where the expiring roll is supported in a first roll supporting position on the roll unwind stand, where the new roll is initially supported in a second, roll supporting position on the roll unwind stand above the plane of the path of the web from the expiring roll as the web from that expiring roll runs through the splicer, and where the new roll is moved, after the web has begun to be run off of the new roll, to the first roll supporting position. Examples of such running web storage means and roll unwind stands are a conventional festoon and a turret type roll unwind stand, respectively.
In the past, several different types of butt splicers have been used with turret type, roll unwind stands. These include so-called: "Festoon Butt Splicers," "Flying Lap-Butt Splicers," "Bobst Butt Splicers," and "Travelling Knife Butt Splicers." These types of splicers are generally described in a book entitled: "Rotogravure and Flexographic Printing Presses" by Herbert L. Weiss, that was published in 1985 by Converting Technology Corp., 4771 N. Bartlett Drive, Milwaukee, Wis. 53211. The description of such splicers, found on pages 340-342 of this book, are incorporated herein by reference.
A splicer embodying the present invention is intended to replace an existing butt splicer, Model No. M 44-3, that was manufactured by the Miehle Company of Chicago, Ill. In this existing butt splicer, the leading end of the web from the new roll is fed into the splicer and held, by a vacuum bar, above the web from the expiring roll running along a substantially horizontal path of travel through the splicer. Tape bars are mounted above and below the webs. To prepare for a splice, the operator must slide out the two tape carriers, apply tape to these carriers and then re-slide them back into the splicer. Aligned upper and lower shearing blades are positioned opposite each other above and below the webs. The tape bars are connected with the shearing blades to form upper and lower assemblies that are movable vertically by a first pair of air cylinders. The vacuum bar holding the new web is also mounted as a part of the upper assembly and is supported so that it can be rotated out of its initial, new web holding position.
When a splice is initiated, clamp bars, actuated by other air cylinders, clamp the web from the expiring roll downstream from the point where the splice is to be made and clamp the webs from the new roll and the expiring roll upstream from the splice. The shearing blades are then moved vertically by the first pair of air cylinders to cut the entire new and old webs, at one time, on a common line. The shearing blades are then retracted and indexed so that the tape bars are now located directly opposite each other above and below the cut line of the new and expiring webs. The tape bars are then brought together by the first pair of the air cylinders. The vacuum bar, still holding the trimmed downstream end of the new web, is rotated from its initial position to keep this trimmed end out of the taping process. After the taped bars have met and forced the tapes together over the splice, the taped bars are retracted, and indexed back to their original positions. Thereafter the clamp bars are retracted and the spliced web begins moving along its path of travel.
This existing splicer has several significant disadvantages. The shearing blades must be perfectly aligned across the entire width of the new and expiring webs or they will not shear properly. This will result in a missed splice. To a large extent, the shearing blades rely on the piston rods and bushings for proper alignment. As the bushings wear, it becomes increasingly difficult to hold this needed alignment between the shearing blades.
Further, after the new and expiring webs are sheared, their sheared ends tend to drop down during the indexing of the shearing blades and the tape bars. This increases the chances of the ends of the webs being improperly aligned when brought back up during the taping process. Enormous pressure is also required to tape the webs because the tape is applied across the entire width of the webs at the same time.
The existing splicer is relatively slow. A number of extra mechanical movements are involved in making a splice. Moreover, the extra mechanical movements require many movable parts and mechanisms that are subject to wear and are difficult to control and service. Additionally, there is less operator safety due to the "guillotine" nature of the shear blades and taping assemblies.
More specifically, the existing splicer is difficult to set up, and an operator must have significant skills and experience to do it properly. The shearing blades were quite expensive, and routinely have to be changed. Additionally, the time required to complete a splice is about four seconds. This, of course, reduces the speed at which the splice may be performed with a given amount of web storage.